Myocarditis in mice infected with Coxsackie virus B3.

Perimyocarditis in the heart of BALB/c mice infected with Coxsackie virus group B type 3 (CB3) was studied to determine whether it is limited to the right perimyocardium and to show whether or not perimyocarditis or myocardial lesions are produced in both left and right ventricles. CB3 was recovered from the heart on days from 2 to 13 after inoculation, but thereafter no virus was isolated from any part of the heart. Histopathologically, from days 1 to 4, hyaline or granular degeneration and necrosis of the muscle fibres with or without calcium deposits and an inflammatory mononuclear cell infiltration was limited to the right perimyocardium. On days 6 to 18, however, degeneration and necrosis of the muscle fibres and an inflammatory mononuclear cell infiltration were found not only in the right perimyocardium, but also in both left and right ventricular wall, the left perimyocardium, both right and left endomyocardium and the septum. In the right ventricular lesions, the incidence and intensity of the histopathological changes in the perimyocardium were greater than those in the muscular layer or septum. In contrast, in left ventricular lesions, the incidence and intensity of the histopathological changes in the muscular layers were greater than those in the peri- and endo--cardium. It is inferred, therefore, that the right perimyocardium and left ventricular wall are more susceptible to CB3 infection than right ventricular wall or left peri- and endocardium. It is concluded that CB3 can produce not only right-sided perimyocarditis, but also both right and left ventricular lesions and endocardial or septal changes in the mouse heart.     

Cardiovascular lipid accumulation with Coxsackie B virus infection in mice

The authors used a myocarditic coxsackievirus B3 infection in Balb/c mice to investigate cardiovascular lipid accumulation and whether a cholesterol-enriched diet influences the development of the myocardial inflammatory reaction. It was found that, seven days after CB3 infection, the accumulation of 14C-cholesterol increased by 75% (P less than 0.001) in the heart and by 92% (P less than 0.001) in the aorta. This infection also caused extensive inflammatory lesions (4.5% of tissue section area) and lipid accumulation in the myocardium seven days after inoculation. Seven weeks on a 1% cholesterol-enriched diet did not affect the myocardial area damaged (3.9%), the lethality, or immune cell activity (T, B, and natural killer [NK] cells). The response pattern of myocardial lymphocyte subpopulations was studied with an immune histochemical staining technique. The number of Mac 2+ (macrophages), class II expressing cells, or the T cytotoxic, suppressor/T helper cell ratio was not changed by the cholesterol diet. The number of class II cells tended to increase (38%) with cholesterol and was positively correlated (P less than 0.001) with the Mac 2 expression regardless of the cholesterol diet. Although moderate diet-induced hypercholesterolemia did not alter host response to viral infection, these results support the idea that virus and immune cells may cooperate and play a role in arterial and myocardial lipid accumulation, possibly acting as initiating factors for atherosclerosis.     

Myocarditis in mice infected with Coxsackie virus B3

Perimyocarditis in the heart of BALB/c mice infected with Coxsackie virus group B type 3 (CB3) was studied to determine whether it is limited to the right perimyocardium and to show whether or not perimyocarditis or myocardial lesions are produced in both left and right ventricles. CB3 was recovered from the heart on days from 2 to 13 after inoculation, but thereafter no virus was isolated from any part of the heart. Histopathologically, from days 1 to 4, hyaline or granular degeneration and necrosis of the muscle fibres with or without calcium deposits and an inflammatory mononuclear cell infiltration was limited to the right perimyocardium. On days 6 to 18, however, degeneration and necrosis of the muscle fibres and an inflammatory mononuclear cell infiltration were found not only in the right perimyocardium, but also in both left and right ventricular wall, the left perimyocardium, both right and left endomyocardium and the septum. In the right ventricular lesions, the incidence and intensity of the histopathological changes in the perimyocardium were greater than those in the muscular layer or septum. In contrast, in left ventricular lesions, the incidence and intensity of the histopathological changes in the muscular layers were greater than those in the peri- and endo--cardium. It is inferred, therefore, that the right perimyocardium and left ventricular wall are more susceptible to CB3 infection than right ventricular wall or left peri- and endocardium. It is concluded that CB3 can produce not only right-sided perimyocarditis, but also both right and left ventricular lesions and endocardial or septal changes in the mouse heart.     

Persistent infection caused by the Coxsackie B3 virus in adult mice

A model of persistent infection with Coxsackie B-3 virus was developed in adult mice with clinical manifestations of the disease and long-term (up to 13 months) excretion of the causative agent. The method of multiple organ cultures was shown to be suitable for isolation of the persisting enterovirus. The presence of persistent infection was confirmed by the detection of IgM antibody in repeated daily examinations of the animals for 4 months. It seems to be expedient to use this model for investigations of the pathogenesis and methods of treatment of persistent Coxsackie B-3 infection in experimental animals.     

Macrophage disappearance reaction in mice during an infection caused by Coxsackie B3 virus

Intraperitoneal inoculation of 2 1/2-3-month-old male BALB/c mice with Coxsackie B3 virus in a dose of 10(7.2) TCD50 was demonstrated to be accompanied by inhibition of the starch-induced exudation of leukocytes into the peritoneal cavity. A decrease in the number of macrophages was observed in 3-day exudates induced at 4 and 21 days but not at 0, 7, and 14 days of infection. The macrophage disappearance reaction showed that the intraperitoneal inoculation of the challenge virus dose (10(7.2) TCD50) was not accompanied at 4-5 hours by changes in the absolute number of macrophages in the pre-existing exudates, but an increase in the absolute number of lymphocytes was observed in the exudates induced at 0, 4, 7, and 14 days of infection, and of polymorphonuclear leukocytes in exudates induced at all the intervals studied. It is assumed that these changes, depending on the period of infection, may be determined by immunological and non-immunological mechanisms.     

Studies on the pathogenesis of atrial myocarditis in mice infected with Coxsackie virus B3.

Coxsackie virus B3 (CB3) was inoculated intraperitoneally into BALB/c mice to determine whether atrial myocarditis is due primarily to virus multiplication in the atrial myocardium or is secondary to the effects of virus multiplication in the ventricular myocarditis. Ventricular changes were observed in 15 (71%) out of 21 mice. The lesions consisted of hyaline or granular degeneration and necrosis with or without calcium deposits of the muscle fibres and inflammatory mononuclear cell infiltration. Histopathological changes in the atrial myocardium were found in 14 (67%) out of 21 mice. The lesions in the atrial myocardium were oedema or thickening of the endocardium, degeneration and necrosis of the muscle fibres and inflammatory mononuclear cell infiltration. The incidence and degrees of intensity of the histopathological changes in the atrial myocardium were less than those of the ventricular myocardium in mice inoculated with CB3, but no difference in the nature of the histopathological changes between the atrial and ventricular myocardium were observed. A high virus titer was found in the atrial myocardium as well as in the ventricular myocardium, and virus antigen was detected in the degenerating or necrotizing muscle fibres in the atrial myocardium by immunofluorescent technique. It is clear that CB3 could produce not only ventricular myocarditis, but also atrial myocarditis. We conclude, therefore, that damage of the atrial myocardium is due to direct action of the virus.     

Characterization of anti-heart antibodies in mice after infection with coxsackie B3 virus

Coxsackie virus B3 (CVB3) infection results in a marked inflammatory response and the production of autoantibodies to cardiac antigens, with cardiac myosin heavy chain documented to be the most immunogenic antigen. The present study investigated the temporal appearance of anti-heart antibodies in mice after mock infection or infection with an attenuated variant of CVB3 or wildtype CVB3 by SDS-PAGE and Western blotting. Further characterization of the autoantigens was carried out using 2D electrophoresis followed by Western blotting. Mice infected with wildtype CVB3 demonstrated high levels of IgG anti-heart antibodies, reacting predominantly with myosin heavy chain but also with numerous other myocardial proteins. Significant increases in anti-myosin heavy chain, anti-actin, and anti-tropomyosin antibodies were seen in wildtype-infected mice as early as day 7 postinfection compared to those mice that were mock infected or infected with attenuated virus. Characterization of other antigens revealed novel reactivities against myosin subfragments, heat shock proteins, and desmin and its subfragments.     

Studies on the pathogenesis of atrial myocarditis in mice infected with Coxsackie virus B3

Coxsackie virus B3 (CB3) was inoculated intraperitoneally into BALB/c mice to determine whether atrial myocarditis is due primarily to virus multiplication in the atrial myocardium or is secondary to the effects of virus multiplication in the ventricular myocarditis. Ventricular changes were observed in 15 (71%) out of 21 mice. The lesions consisted of hyaline or granular degeneration and necrosis with or without calcium deposits of the muscle fibres and inflammatory mononuclear cell infiltration. Histopathological changes in the atrial myocardium were found in 14 (67%) out of 21 mice. The lesions in the atrial myocardium were oedema or thickening of the endocardium, degeneration and necrosis of the muscle fibres and inflammatory mononuclear cell infiltration. The incidence and degrees of intensity of the histopathological changes in the atrial myocardium were less than those of the ventricular myocardium in mice inoculated with CB3, but no difference in the nature of the histopathological changes between the atrial and ventricular myocardium were observed. A high virus titer was found in the atrial myocardium as well as in the ventricular myocardium, and virus antigen was detected in the degenerating or necrotizing muscle fibres in the atrial myocardium by immunofluorescent technique. It is clear that CB3 could produce not only ventricular myocarditis, but also atrial myocarditis. We conclude, therefore, that damage of the atrial myocardium is due to direct action of the virus.